Treatment of argentiferous sulphide ores



Patented Dec. 1925.

UNITED STATES PATENT OFFICE.

' mum: E. ELMORE, or BOXMOOR, ENGLAND, ASSIGNOR T NIELS c. CHRISTEN- sun, or SALT LAKEoI'rY, UTAH.

TREATMENT or Anennrrrrnou's sunrrnnn onus.

.10 Drawing.

.To all whom it may concern Be it known that I, FRANK EDWARD EL MORE, a subject of the King of Great Britain, residing in Boxmoor, England, have invented certain new and useful Improvements in the Treatment of Argentiferous Sulphide Ores, of which the following is a specifica-. tion.

This invention relates to improvements in lo the treatment of argentiferous sulphide ores, concentrates and the like (hereinafter called ores) for the separation and recovery of the silver and other metals contained therein. Aknown process (hereinaftercalled the acid brine process) for the separation of lead and zinc 'from ores in which thesemetals co-exist in the form of sulphides,

whichprocess consists in treating the finely divided ore with ,a'hotstrong' solution of no sodiumchloride-to which a sufiicient quantity of sulphuric or hydrochloric acid or an alkali-bisulphate is added, whereby the lead is caused to pass into solution whilstsubstantially the whole of the zinc sulphide 'remains undissolved, the hot solution obtained beingse arated" from the residue containing salt.

Ores suitable for treatment by the aforesaid process fre uently contain appreciable proportionsof silver, the eflicient recovery of which by hitherto known methods of ex-' traction is attended with difliculties. On treatment of the ore with acid brine only a portion of the silver passes into solution along with the lead. This portion may be recovered by known methods, but the balanceremains undissolved with the zinc sul- 40 phide in the residue. The object of the present invention is to provide a satisfactory method of separating and recovering in form suitable for metallurgical treatment substantially the whole of-the silver and also,

if desired, the lead andzinc contained in such ores. In certain cases the ore may be poor in lead and zinc and yet rich enough in silver to be worth treatment for the recovery of this metal alone. v According to this invention the ore is first heated to about a dull heatunder such I conditions that the: -zinc sulphide remains substantially un-decomposed, and, is then subjected to the-acid brine process. There Application filed June 9,

- chloride.

both. the undlssolved zin'c sulphide and tooledto cause a partial crystallization of the lead 1922. Serial No. 567.203.

inafter, used in the specification and claims I intend to include hydrogen chloride, a metallic chloride'whichgives an acid solution 1 with water, and such metallic chloride asso- 'ciated with hydrogen chloride. I prefer to i use a saturated solution of. sodium chloride or a solution containing approximately 35' per cent by Weight of calcium chloride -or magnesium chloride, to which has been addedasmall percentage (varying with the composition of the material to be leached) ofcupric chloride, hydrochloric acid, or

The following, example illustrates the invention: I

An argentlferous lead-zlnc ore from Burmah is heated in a closed pot to 650 C. for

'1 hour. After cooling and, if necessary, grinding, 1t istreated by the acidbrine process, that isto say, 20 kilos of the ore which has been thus heated, crushed to pass through a 100 mesh standard sieve, are stirred in an earthenwaresteam-heated vessel with 100 litres of a saturated solution of common salt and the mixture is heated to about C. 6 litres of sulphuric acid of.

1.84 specific gravity are gradually run into the vessel, 'the heating being continued. When the evolution ofsulphuretted hydrogen has practically ceased, the hot brine is separated from the insoluble matter. The

latter contains zinc sulphide and some of the silver, the rest of the silver and the bulk of the lead having been removed in the brine to be recovered in known manner.- The at ntiferous residue containing zinc sulphi e is then treated with a solvent consistlng of a hot, strong solution of calcium chloride containing about 35 per cent of 'laCl, and about 5 per cent of cupric chloride, whereby subfstantially all the silver is extracted from the residue; thus a residue containi 8.25

ounces of silver per ton, when leache with the calcium chloride-cu ric chloride solvent, yielded 94 per cent of t e silver to the latter.

In another example an ore containing 21.9 ounces of silver per ton was heated to 450 C. for 45 minutes and then treated by the acid brine process in similar manner to that described 1n the foregoing example; the residue was leached at 95100 C. for half an hour with a solution containing 35 per cent of calcium chloride and about 5 r cent of commercial concentrated hy rochloric acid; and the final zinciferous residue was found to contain less than 5 per cent of the silver originall present in the ore.

Having thus descri ed the nature of the ,said invention and the best means I know of carrying the same into practical efl'ect,'I claim v.

1. Process of treating argentiferous leadzinc sul hide ores, consisting in heating the ore to a out a dull red heat under such conditions that the zinc sulphide remains substantially undecomposed, then subjecting the ore which has been thus heated to the acid brine process, and then leachin the at ntiferous zinc sulphide residue 1: us obtained by means of acid chloride brine solvents which extract the silver therefrom and leave chloride containing acid chloride, which extracts the silver therefrom and leaves the zinc sulphide substantially undissolved.

3. Process of treating argentiferous leadzinc sulphideores, consisting in heating the ore to a cut a dull red heat under such conditions that the zinc sulphide remains-subslantially undecomposed, then subjecting the ore which has been thus heated to the acid brine process and then leachin the ar en-- tiferous zinc sulphide residue t us obtained b means of a solution of alkaline-earth chlo-v rlde containing hydrogen chloride, which extracts the silver therefrom and leaves the zinc sulphide substantiall undissolved.

In testimony whereof have signed my name to this specification.

- FRANK E. ELMORE. 

